The protection of crops from undesirable weeds which can interfere with crop growth has long been a goal in agriculture. One approach which has been taken to achieve this goal is the development of selective herbicides which can control weeds without exhibiting unacceptable phytotoxicity to the crops sought to be protected. More recently, crops have been protected from weeds by genetically modifying the crop to be resistant to a non-selective herbicide (such as glyphosate or glufosinate) and applying such herbicide over the top of such crops. Unfortunately, this latter approach has led to the development of herbicide tolerant weeds, with the result that there is still a need for a means of selectively controlling undesirable vegetation in fields.
U.S. Pat. No. 4,405,357 discloses certain 3-isoxazolidinones which exhibit desirable selective herbicidal activity. Specifically, such compounds are shown to be effective in controlling grassy and broadleaf species while leaving legumes, particularly soybeans, unaffected. Among the compounds specifically disclosed in this patent are 2-(2,4-dichlorophenyl)methyl-4,4-dimethyl-3-isoxazolidone (Compound 22) and 2-(2,5-dichlorophenyl)methyl-4,4-dimethyl-3-isoxazolidone (Compound 87). Both such compounds are demonstrated to be effective against a number of weeds; including, for one or both of such compounds, (a) monocot grasses such green foxtail, barnyard grass, goose grass, and crabgrass; and (b) dicot species such as chickweed, lambsquarters and velvetleaf.
It has now been discovered that despite such desirable activity, particularly on monocot grass species, both 2,4-Cl and 2,5-Cl may be employed as selective herbicides on grassy monocot crops including corn, rice, sorghum and sugarcane; as well as on the brassica species canola, without causing an undesirable amount of phytotoxicity to such crops. Moreover, such compounds exhibit reduced volatility relative to other 3-isoxazolidinone herbicides such as clomazone.